Urochloa ruziziensis cover crop increases the cycling of soil inositol phosphates
Urochloa ruziziensis cover crop increases the cycling of soil inositol phosphates
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DOI：
10.1007/s00374-018-1316-3
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发表时间：
2018-11-01
影响因子：
6.5
通讯作者：
Rosolem, Ciro A.
中科院分区：
文献类型：
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作者：
Almeida, Danilo S.;Menezes-Blackburn, Daniel;Rosolem, Ciro A.
Ruzgrass(Urochloa Ruziziens)是巴西常用的一种覆盖作物，其根部分泌高浓度的有机酸，因此有望调动土壤中的有机磷，如肌醇磷酸盐。然而，这是否只有在缺磷的情况下才会发生，目前还不清楚。具体地说，我们的目的是验证这样的假设，即在两个不同的磷水平下种植草莓可以加速肌醇磷酸盐的降解。为了研究这一点，我们在一个9年的田间试验中研究了土壤有机磷，在大豆(Glyinemax)淡季，无论有没有添加磷，处理都包括草莓或休耕。用NaOH-EDTA提取有机磷，然后用次溴酸盐氧化比色法定量植酸酶可降解的有机磷和肌醇六磷酸根，并用高效液相色谱分离。施磷量比对照提高80%左右。鲁吉拉斯降低了植酸酶活性磷和肌醇六磷酸的浓度，但仅在施磷土壤中，未鉴定的肌醇磷酸盐也相应增加，可能代表低级酯。我们推测，在施磷的情况下，根分泌物的释放增加了根分泌物的释放，从而促进了肌醇磷酸盐的分解，从而促进了植酸酶对肌醇磷酸盐的分解，这是由于在肥力较高的处理中，红豆草的生产力较高。我们的结论是，覆草可以促进顽固土壤有机磷的循环，但只有在肥力提高到足够的水平以确保作物高产的情况下才能实现。
Ruzigrass (Urochloa ruziziensis) is a cover crop that is commonly used in Brazil and exudes high concentrations of organic acids from its roots, and is therefore expected to mobilize soil organic P such as inositol phosphates. However, it is not known if this can occur only under P deficient conditions. Specifically, we aimed to test the hypothesis that the degradation of inositol phosphates is increased by growing ruzigrass at two different P levels. To investigate this, we studied soil organic P in a 9-year-old field experiment, with treatments consisting of ruzigrass or fallow during the soybean (Glycine max) off-season, with or without P addition. Organic P was extracted in NaOH-EDTA, followed by colorimetric quantification of organic P hydrolysable by phytase, and myo-inositol hexakisphosphate by hypobromite oxidation and HPLC separation. Ruzigrass dry matter yield increased by about 80% with P application. Ruzigrass reduced the concentration of phytase labile P and myo-inositol hexakisphosphate, but only in soil receiving P. A corresponding increase in unidentified inositol phosphates, presumably representing lower-order esters, was also observed after ruzigrass in soil with P application. We deduce that the degradation of inositol phosphates under ruzigrass with P application is due to greater ruzigrass productivity in the more fertile treatment, increasing the release of root exudates that solubilize inositol phosphates and promote their decomposition by phytase. We conclude that ruzigrass cover cropping can promote the cycling of recalcitrant soil organic P, but only when fertility is raised to a sufficient level to ensure a productive crop.